The present invention relates to an apparatus for producing discontinuous cuts in a weblike material fed continuously through said apparatus. The invention also relates to a method for making discontinuous transverse cuts in a continuously fed weblike material.
More particularly, but not exclusively, the present invention relates to a cutting device for cutting transversely at selectable points or portions a web of board fed to a slitter/scorer for the manufacture of slit and scored sheets of board.
In many industries there is a need to cut a weblike material, e.g. a web of board, paper, fabric, plastic or otherxe2x80x94fed continuously along a longitudinal path of forward travelxe2x80x94in predetermined and selectable portions or points along the width of the weblike materialxe2x80x94often without interrupting the material, i.e. without generating two completely separate pieces of material.
This requirement occurs particularly in the industry of the manufacture of slit and scored sheets of corrugated board for the manufacture of boxes. In installations for slitting and scoring corrugated board webs for the manufacture of sheets from which boxes or the like will be made up, a web of corrugated board is fed continuously to a slitter/scorer, where the web is slit and scored longitudinally in predetermined positions and the slit and scored web is fed to a transverse cutting system to produce the individual sheets. Transverse cutting is performed in some cases by two (or more) cutters arranged at different heights or levels, in which case it is necessary to divide the path of the board web downstream of the slitter/scorer so that separate portions of board are fed to the separate levels at which the cutters are located. The longitudinal slitting of the board is performed by the blades of the slitter/scorer.
When one job is terminated and the next job is to be begun, the position of the longitudinal slitting and scoring lines produced on the board is altered so that the transverse dimensions of the pieces of board fed to the different heights or levels at which the transverse cutters are situated change. Where the job changeover occurs, a transverse cut must be made in order to connect up the two longitudinal slits of the new job and the old job, ensure that the board does not tear at this point, and achieve uniformity in the tensile force applied to the weblike material.
The position in which the transverse cut line is effected is variable. Moreover, the transverse cut line must be short enough not to interrupt the strips of boards in the transverse direction as these would otherwise suffer skidding and loss of alignment during their conveyance.
A variety of different systems have been investigated in order to solve these problems either wholly or partly. For example, U.S. Pat. No. 5,297,461 discloses a transverse cutting apparatus in which a cutting cylinder comprising a continuous blade extending all the way along the length of the cylinder acts in combination with an opposing cylinder carrying opposing pads whose angular positions around the opposing cylinder can be selected by an angular movement about the axis of the opposing cylinder. By this means one or more of the opposing pads can be brought selectively into position such as to act in combination with the cutting blade. At the points at which the pads act in combination with the cutting blade the board is cut, whereas at points at which there is no pad underneath the cutting blade the board is not cut.
U.S. Pat. No. 5,152,205 discloses a system similar to the previous system, in which the blade mounted on the cutting cylinder acts in combination with a series of lower pads that can be selectively raised or lowered in defined locations of the width of the board where the cut lines are produced.
The resulting cut is not accurate and there is a risk that the board may also be cut in locations where the cutting blade does not act in combination with an opposing lower pad. Furthermore, with these systems there is no way to select the locations to be cut with sufficient accuracy, nor to prevent transverse interruption of the strips of board.
European patent application No. 98 830 449.9 (publication No. EP-A-0 894 583) and the corresponding U.S. application Ser. No. 09/124,017 by the same applicant disclose an improved system in which a blade mounted on a rotating cutting cylinder acts in combination with a backing consisting of a pad mounted on an opposing cylinder. The pad can be moved longitudinally and angularly with respect to the axis of the opposing cylinder and also is so shaped that it is possible to produce, in combination with the blade, cut lines of the desired length and position. In addition, in this system the cutting tools of the slitter/scorer can be operated independently of each other. In this way it is possible to interrupt all the longitudinal slit lines of the old job and new job with the exception of the two central lines which in both jobs divide the board into the two portions which must be directed to the two levels where the cutters are located. As a result a job changeover region is generated containing only the two central slit lines which are joined by a cut approximately at right angles to the direction of forward travel of the board. This ensures the continuity of all the strips into which the board is divided.
U.S. Pat. No. 4,007,652 discloses a system in which the two intermediate longitudinal slit lines that divide the board into the two portions fed to the two separate levels where the transverse cutters are located are joined together by an inclined cut produced by a water nozzle traversing at right angles to the feed direction of the weblike material. The same solution is disclosed in EP-A-0 607 084. The use of a water nozzle for the inclined transverse cut has some advantages, including that of avoiding the complete transverse cut through one or more of the strips into which the board web is divided. This apparatus, however, has the disadvantage of high cost and requires a high level of attendance during operation because of the criticality of the water cutting system.
EP-A-0 737 553 discloses a system in which water nozzles are used to cut the lateral trimmings, the purpose being to obtain a continuous trimming along both sides of the board.
The present invention includes a rotating cutting cylinder and an opposing member, wherein the cutting cylinder is fitted with a plurality of blade segments distributed along the length of the cutting cylinder and connected to one or more actuators for producing a movement of selective extension and retraction of said blade segments with respect to said cutting cylinder.
Depending on the positions of the central slit lines to be joined by the transverse cut, the actuators extend one or more blade segments in the desired position to effect the selective localized cut through the weblike material. The cut may preferably be at right angles to the direction in which the weblike material is fed, or slightly inclined, e.g. as a consequence of a slightly helical arrangement of the blade segments on the cutting cylinder. However, cuts inclined relative to the feed direction are not ruled out.
In the following description and in the appended claims, reference will frequently be made to a pair of central lines that are joined by the transverse cut produced by the blade segments mounted on the cutting cylinder. It should however be noted that the term xe2x80x9ccentralxe2x80x9d is to be understood here as meaning exclusively. a position which divides the weblike material into longitudinal pieces intended to be fed to transverse cutters located at different levels. In light of this, the so-called central lines may be in any intermediate position relative to the widths of the weblike material, and may for example be much closer to one longitudinal edge than to the other. Also it should be realized that, although the remainder of the text will refer primarily to a system in which the weblike material is divided into longitudinal strips which are then fed onto two separate levels, the inventive concept is not limited to this embodiment. On the contrary, the same concept can be extended to the scenario in which the weblike material is divided into a plurality of strips or groups of strips which are then sent to a corresponding plurality of different levels for the transverse cut. In this case the transverse cut joining together the longitudinal so-called central slit lines will be repeated on each pair of longitudinal slit lines corresponding to the portion containing the division between adjacent pieces of weblike material directed to different levels. Indeed, the cutting apparatus according to the invention presents almost no limits in terms of the number, length and position of the transverse cut lines.
In practice, it is advantageous to have one actuator for each blade segment, or for a limited number of contiguous blade segments. The actuators can be housed in an axial cavity inside the cutting cylinder. They may comprise one piston/cylinder actuator (generally of pneumatic type) for each blade segment. The possibility of also using hydraulic type piston/cylinder actuators is not ruled out, although this adds complications from the engineering point of view. Alternatively, mechanical, electromechanical, electromagnetic or other types of actuators can be used.
For example, each blade segment may be controlled in its movements of extension and retraction by an electromagnet with a mechanical return member. Alternatively, electric motors may be used with suitable mechanical drives, e.g. gears. A mechanical actuating apparatus may use a mechanism employing a cam or eccentric and a tappet or rocker arm, with a double-acting cam or eccentric, with a grooved cam profile or with elastic return members.
If a piston/cylinder actuator is used, this may act directly on a pivoting member carrying the blade segment, as in the example which will be described below, but the possibility of also using more complex arrangements in which the piston/cylinder actuator or equivalent means acts on the component carrying the blade either directly, or via a series of levers and drives, is not ruled out.
The piston/cylinder actuators, the electric motors and other equivalent actuators usable in the present application include both linear and rotary actuators.
Preferably, for reasons both of cost and of reliability, simplicity and bulk, linear pneumatic piston/cylinder actuators are currently preferred.
The cutting cylinder may be provided with a continuous rotational motion and may be activated only at the moment when the job changeover is required, by the actuation of the blade segment extender actuators. However, this is not as a rule required and the cutting-cylinder may remain stationary throughout the processing of a job, being rotated (preferably for one revolution only) at the conclusion of the processing of one job and at the start of the next process.
The cutting apparatus may be placed upstream or downstream of the system that slits the board longitudinally, as the transverse cut can also be produced by the blade segments in a weblike material not yet divided into longitudinal strips. By positioning the cutting apparatus upstream of the system that slits the board longitudinally, i.e. in practice upstream of the slitting and scoring stations, it is possible to use the same cutting apparatus as an auxiliary cutter in order to introduce, when required, a complete transverse cut across the weblike material. This necessity may occur, for example, where the weblike material coming from the upstream manufacturing machine (i.e. for example from the corrugator) varies in width. If this happens, where the change of width of the weblike material occurs, a complete transverse cut must be made and the lateral trimmings be reintroduced into the suction mouths. In conventional installations this complete transverse cut is performed by an additional machine provided expressly for this purpose and situated upstream of the slitter/scorer. With the cutting apparatus according to the invention it is possible to make both the complete transverse cut, and the partial transverse cut that joins the central longitudinal cut lines, with the same apparatus. For this purpose all that is required is an appropriate control of the blade segments which, in the first scenario, will all be extended from the cutting cylinder.
The complete transverse cut may also be required, for example, in order to discard a piece of weblike material. In this case the cutting apparatus can perform this function even if positioned downstream of the slitter/scorer unit.
The possibility is not ruled out that the cutting apparatus may be placed in other intermediate positions, such as between a longitudinal slitting station and a succeeding longitudinal scoring station, or between a scoring station and a slitting station arranged downstream of the scoring station. Generally speaking, although the arrangement in which the cutting apparatus is upstream of the slitter/scorer is preferable for the abovementioned reasons, it can be in any intermediate position between the feed point of the weblike material from the upstream manufacturing station (or from a supply roll) and the point at which the longitudinally slit weblike material is divided onto a plurality of levels.
The opposing member may take the form of a fixed pad, or of a continuous belt traveling over a supporting system in the same direction as the direction of forward travel of the weblike material, so that it supports the weblike material as it advances during the cut. Preferably, however, the opposing member is a rotating cylinder suitably covered with a soft material so as not to damage the blade while it is cutting. Nonetheless, the use of a revolving opposing blade as the opposing member, as in other shear cutting systems, is not ruled out.
To obtain an accurate and easily controllable movement, in an especially advantageous embodiment each blade segment is supported by a pivoting part hinged about a hinge axis, the extension and retraction of said blade segments being produced by a pivoting movement of said pivoting part about said hinge axis. The hinge axis may be parallel or approximately parallel to the axis of the cutting cylinder. In reality, it being advantageous (for reasons explained later) that the blade segments be arranged in a helical manner, the hinge axes of the corresponding supporting pivoting parts will be inclined, if only slightly, relative to the axis of the cutting cylinder.
In an especially advantageous embodiment, the hinge axis is external to the cutting cylinder. However, an arrangement in which the hinge axes of the blade segments are internal to the cutting cylinder is not ruled out.
In order to reduce the stresses on the controlling actuators of the individual blade segments and ensure that they do not retreat during cutting, it may advantageously be arranged that a stop is connected to each pivoting part to absorb at least some of the stresses exerted on the corresponding blade segment during the cutting. In practice it is also useful for each blade segment to be situated, when in its extended position, between the hinge axis of its pivoting part and the corresponding stop.
The apparatus according to the invention can be used to carry out a method for producing discontinuous transverse cuts in a weblike material fed continuously along a longitudinal feed path, comprising the following stages:
arranging a rotating cutting cylinder on a first side of said longitudinal path;
arranging an opposing member on a second side of said path;
selecting at least one portion of said weblike material along its width; and
cutting said weblike material along said at least one selected portion without interrupting the weblike material; characterized in that a plurality of selectively extendable and retractable blade segments are arranged on the cutting cylinder; and one or more of said blade segments is/are selectively extended toward said at least one selected portion in order to cut said weblike material transversely in the selected portion.
Other advantageous features and embodiments of the invention are indicated in the accompanying claims.